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TMS570 DGNS and AGND seperation

suresh B91852
Intellectual 300 points

Hi can you please let me know the reason of not seperating GND and AGND in the development board.TMS570LS31x_HDK_Schematics.

 

Kindly clarify the reason behind this.

If i insist to short both let me know if there are any constraints i need to consider .

 

Regards

Suresh

  • 0
    TI__Guru**** 200206 points

    Hi Suresh,

    It is a very good question without a simple answer. Some people like to use separate analog and digital planes and  connect them at one point, but I like to use one plane. There are 2 basic principles of EMC: 

    1. Current should be returned to their source as locally as possible, or through the smallest possible loop area.

    2. should have only 1 references for a system.

    If we provide 2 references for a system, we create a dipole antenna; If we do not return current locally and compactly, we create a loop antenna. Both are undesirable results. 

    Although the split plane method can be made to work, it have many potential problems. One major problem is that you can not route a trace over the split in the plane. If you do so, both the radiation and crosstalk will increase dramatically. Partition and routing are more important than the isolation of the ground plane. This is only my opinion. 

    Regards,

    QJ

  • 0
    TI__Guru**** 200206 points

    Hi Suresh,

    It is a very good question without a simple answer. Some people like to use separate analog and digital planes and  connect them at one point, but I like to use one plane. There are 2 basic principles of EMC: 

    1. Current should be returned to their source as locally as possible, or through the smallest possible loop area.

    2. should have only 1 references for a system.

    If we provide 2 references for a system, we create a dipole antenna; If we do not return current locally and compactly, we create a loop antenna. Both are undesirable results. 

    Although the split plane method can be made to work, it have many potential problems. One major problem is that you can not route a trace over the split in the plane. If you do so, both the radiation and crosstalk will increase dramatically. Partition and routing are more important than the isolation of the ground plane. This is just my opinion. 

    Regards,

    QJ